Know Your Limit
by nell-90
Summary: Sherlock realises that John more or less relies on him to maintain his figure and becomes increasingly disgusted by weight gain. He decides to monitor John's figure and begins to put a rather harsh strain on John's mentality and his relationship with food. Warning: weight issues and implication of eating disorder
1. Chapter 1

**Author's note: This is my first fanfic so by all means feel free to critique as much as you like but be aware that I'm totally new to this.  
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**WARNING: This fic contains reference to weight issues and manipulation regarding that area. If you have any eating disorder or the like that could possibly be triggered by this I would recommend that you don't read it (this chapter not so much but definitely in the chapters to come)**

* * *

Sherlock Holmes and John Watson were between cases. In fact, they had not taken a case for almost two weeks and Sherlock was interchanging between lying on the couch in a manner that could only be described as catatonic, and racing round 221B in a manic state desperately trying to find something to do. At this point it was the former and John let out an unnoticeable sigh of relief for the peace and quiet after a hectic past 24 hours. He was sitting at the table in the living room sifting through the comments on the blog in the hopes of finding something – _anything_ – to distract Sherlock.

Sherlock was lying on the couch in his thinking pose. He knew that John thought something had caught his mind and it was one of those moments when the good doctor was right. Something _had_ caught Sherlock's mind. It had been 13 days since their last case. For 13 days they had not left the flat. John had gone out to grab a few basic supplies but other than that they had been sitting around waiting for the next offer of a case. Sherlock ran a critical eye along the width of John's waist. There was no noticeable change to the untrained eye but Sherlock was anything but untrained. There was a very slight stretch of the terrible jumper around John's midsection and Sherlock could imagine a similar strain on the button of his trousers. _Weakness _thought Sherlock. _He relies on me to exercise him_. Without taking his eyes off John he snaked his hand under his own dressing gown and lightly touched each of his ribs before settling on his hipbone. _Can't have him getting fat now can we?_ he thought.

* * *

John had been awake for far too many hours. He didn't really want to think of the exact number. There was no point trying to sleep when Sherlock was manic. As soon as his head hit the pillow and he began to drift from consciousness he would hear the unmistakable sound of a tiresome experiment or, on the better nights, the tuneful – but loud – melodies from Sherlock's violin. So he stayed awake until Sherlock retreated to the couch and encapsulated himself in his mind palace. Now there was peace and quiet and, of course, he was beyond the tired feeling. He would have to wait for the next wave of sleepiness. John suddenly rose from his seat at the table and walked to the kitchen, unaware that Sherlock was still eyeing him. Sherlock's view was obstructed when John crossed the threshold of the kitchen but he could still hear the telltale sound of the fridge opening and the flick of the kettle.

"Want a cuppa?" John called.

Sherlock remained silent.

"If you don't answer me I'm going to assume it's a no"

"Assume away," said Sherlock stiffly.

John brewed his own cup of tea and fixed himself a sandwich made of some defrosted bread he found in the freezer and leftover cold meat that Mrs. Hudson had brought over for them. He also gave in to temptation and grabbed a handful of the biscuits left on the bench that seemed safe enough to eat. John returned to the living room and sat down in the armchair with his quick-fix meal. Sherlock's gaze drifted to him and then to the plate perched on his lap.

"You should really consider fibre and vitamins from vegetables over all those carbohydrates," Sherlock said snidely.

John smirked, "yep, thanks for the nutrition advice, Mr. I-Couldn't-Eat-Right-To-Save-My-Life."

"My waistline is in prime condition –"

"It's not about the bloody _waistline_,"

"– Which is more than I can say regarding some."

"It's to do with the –" John's thought was halted as he processed what Sherlock had said. "Hang on, what?"

"John, surely you wouldn't disagree that my physique is widely considered to be better than your own"

John rolled his eyes, "yes, Sherlock, I know that. But it ultimately comes down to different body shapes. I'm not some teenage girl that is going to fuss about stuff like this because her body isn't tall and thin like her friend's."

Sherlock sniffed.

"And I won't even go into everything you should really know already about how body shape isn't a definite indication of health and nutrition."

"Oh of course, please continue to explain, Dr. Watson," snapped Sherlock in his condescending tone often reserved for Anderson.

"I'm not going to have this conversation with you! I'm already familiar with your body's ability to function without food or sleep but I am, believe it or not, a normal human so _get off my back_."

"Fine. Go ahead. I won't be held responsible when you can't keep up with me around the streets of London," said Sherlock as he gracefully stood from the couch and stormed off into the bedroom.

John rolled his eyes again and took a large bite of his sandwich.

Once he had secluded himself behind his bedroom door Sherlock fell to the bed. He began wondering if John actually subconsciously relied on Sherlock to keep him in shape, to keep him healthy. He scoffed at the thought of John trying to accuse him of not understanding nutrition. Sherlock knew how to eat just enough to keep his transport going. Any more than that was unnecessary and should be avoided unless he wanted to experience that awful sluggish feeling as his body tried digesting the extra.

And now his mind drifted back to John's figure. Perhaps he should conduct an experiment to see if John really did rely on him. It would be easy enough to do. Of course they would have another case soon enough and it would be back to running around London chasing criminals, but Sherlock could easily pay a few extra visits to Angelo's. Pick out a few of the creamier pasta dishes or the slightly oilier fried food. Just to see what John would do. The experiment was laid out clearly in Sherlock's mind and he felt the excitement build in anticipation of what results were in store.

* * *

Two months had passed since Sherlock formed The Experiment. Since then he and John had solved a number of cases that had Lestrade and the rest of New Scotland Yard baffled. As always, John watched in awe as Sherlock deduced killers from the type of carpet in a bedroom and kidnappers from residue left on a dining table. Every now and then John would lend his medical opinion and give Sherlock pointers that he thought were helpful enough even though he was well aware that he could not match Sherlock's wind.

So, ultimately, nothing was new. Except there _was_ something new. Sherlock had suddenly taken to being aware of how often a normal person needs to eat. He paused investigations to take John out to lunch and even supplied dinners on most evenings. Of course he always ate so little, keeping predominately to water and nibbling on side dishes. John's concern as a doctor was spiked at this behaviour but was soon subdued as he reminded himself that this wasn't exactly unusual for Sherlock.

After every mealtime Sherlock would catalogue results that he observed. There were multiple things that he looked out for: John's choice and whether or not he took on Sherlock's suggestion, eating speed, John's behaviour following a meal (energised, lethargic), and, obviously, how his body looked.

In the two months of The Experiment, Sherlock identified that John had gained approximately 9 pounds. His belly was very slightly distended beyond the waist of his trousers and there was a very subtle softening of the edges to him. Not enough to be deemed abnormal and not enough for people to comment on, or avoid commenting on. But enough for Sherlock to feel a quiver of horror to realise that yes, John relied on him to maintain his figure.

It was this realisation that compelled Sherlock to discard The Experiment and make a start on The Solution.

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**Thank you so much for reading and sticking to the end of the first chapter. Please leave a comment if you enjoyed it or have any advice. It will really help in shaping future writing. **


	2. Chapter 2

**The more obvious weight issues/control stuff starts in this chapter so consider yourself warned. **

* * *

John was napping in his armchair with his hands settled comfortably on his stomach, the remnants of a cup of tea and a few biscuits on the floor just beside him. 221B was surprisingly peaceful and he was making the most of it. Well, he _was_ until Sherlock suddenly burst out of his bedroom loudly calling his name.

"John, wake up," snapped Sherlock.

John lazily opened one eyelid and glared at him before closing it again. "Not now, Sherlock. Just give me these couple of minutes okay? You were being so quiet before!" he muttered slowly.

Sherlock looked at John with obvious distaste and said something about that being before and it now being now – a relatively common speech that Sherlock drawls when he has decided that he wants something done and a speech that John has taken to ignoring the past couple of times. Upon realising that nothing he was saying was actually getting through, Sherlock vaguely mentioned a fleeting idea that involved testing how fire resistant the kitchen was.

John's eyes flickered open immediately.

"Finally. I will have to remember that experiment for whenever you need to be hurried along."

"Shut up, Sherlock. Now what's so important?" said John in a slightly agitated tone.

"I need you to stand up and take off your jumper and shirt," stated Sherlock.

"You _what_?"

"I need you.. to stand up.. and take off your jumper and shirt."

John knew that Sherlock hated unnecessary repetition and his mocking articulation of every syllable of his sentence made this all too clear. "Why the bloody hell do you need me to do that?"

"Because."

_God, he's a petulant child_ thought John. In the hopes of just getting whatever Sherlock had in stall over and done with, he stood up and pulled off his jumper. He then unbuttoned his shirt and let it fall open.

And Sherlock just stared.

There was a stillness in the air that quickly became uncomfortable as John tried, and failed, to understand why he was standing almost topless while being scrutinised. Sherlock drank in everything that he could see and ever so slightly shook his head.

"This," started Sherlock, poking a pale, thin finger into John's abdomen causing him to jump a little, "is disgusting."

"Oh, fuck off," spat John as he roughly pulled his shirt back together and smacked Sherlock's finger away.

He grabbed his jumper that had been dropped on the floor and began to walk away.

"I'm only trying to help you," said Sherlock matter-of-factly.

"Stick to what you know, Sherlock. It's not people," retorted John before climbing the stairs and slamming his bedroom door.

* * *

By the time the sun had set and the lights on Baker Street began to flicker on, John had still not emerged from his room. He really wasn't in the mood to talk to Sherlock again that day after whatever the hell went down in the living room earlier. It still was not completely clear to John as to what had suddenly gotten into Sherlock that would cause him to have a sudden interest in his body. Sure, Sherlock had always been extremely fit and trim but he was never _obsessed_. He didn't eat on cases but that was never a diet technique – that was simply Sherlock being Sherlock and convincing himself that digesting slowed him down. And yet John valued his opinion, and the sudden outburst made him question himself. He knew that he had put on a small amount of weight since returning to London but it wasn't a big deal at all. He was adjusting to civilian life and it was to be expected. Plus moving in with Sherlock motivated him to eat enough to actually sustain him, which was more than he could say about the time he spent living alone.

John quickly positioned himself in front of the mirror in his room and took off his shirt for the second time that day. He examined himself by turning around and looking at himself from different angles.

_This is so stupid_ thought John. _I am so bloody stupid_.

He ran his hands over his chest and abdomen to try to find anything that Sherlock could have seen as 'disgusting'. He was still solid from his days in the army and there was still a presence of muscle mass. Sure, he was slightly softer round the edges and sure there was a lip of flesh poking out over the waist of his trousers but that was nothing to worry about.

_Is that so? Maybe it is… 'disgusting'._

John shook that thought away quickly.

_Why would Sherlock bother saying it if it wasn't true?_

As if on cue, his door was opened and John turned to meet Sherlock's gaze.

"John, I owe you an explanation," said Sherlock.

"I think an apology is more what you owe me," replied John, suddenly feeling very exasperated.

"I am not sorry for what I said but it is obvious you were hurt by it."

"Deduce that, did you?"

"It's hardly my fault you don't like hearing truth."

"As much as I reckon I'll regret this, please explain what the hell your ridiculous mind has decided now because I have no bloody clue what you have been going on about today," said John keeping his eyes locked on Sherlock's.

Sherlock suddenly closed the large gap between the two of them and stood at a distance that could almost be classed as intimate. John was suddenly very aware of the fact that he was still not wearing a shirt.

"I don't want you getting fat," stated Sherlock simply and without hesitation.

John broke eye contact for a moment and looked off to the side. There was a look of bemusement written in his expression. "I'm sure we can avoid that one pretty easily, Sherlock."

Sherlock began to laugh but his face quickly turned stony again. "Oh yes, you _would_ like to think that, wouldn't you?"

Before he could respond, Sherlock had reached out and held him at the edges of the waist. Had it been anyone but Sherlock, the action would have been amorous. John was feeling incredibly uncomfortable and had still not met the blue-grey eyes again as he tried to convince himself that if he did not look at Sherlock the harsh words that he knew were to follow would not affect him.

"Domestic bliss must suit you, John. You have put on 9 pounds in the past two months."

John bit his lip at the cruel echo of Sherlock's words to Molly. He definitely sympathised with her when it happened but he quickly realised that it was much worse than he imagined on the receiving end of the comment. He also noted that when Sherlock said it to Molly it was almost a statement. No connotation, just pointing out the obvious. Sherlock said it to John with disgust.

His hands moved away from John's waist and tapped him on the stomach. John hated every second of it. His body felt so different under Sherlock's slender fingers than it did under his own hands.

"I want my doctor to be in prime condition," said Sherlock as he touched his stomach in the softest part before continuing. "And I don't want any of _this_ slowing him down."

Then the hands dropped away. John let out a breath he did not realise he had been holding. Sherlock dug into his trouser pocket and retrieved a tape measure.

"Assuming that you are going to rectify the problem, I am going to note your progress," said Sherlock. When he noticed John's confused and slightly shocked face he added, "Consider it an experiment of mine."

John sighed and said nothing, which Sherlock took as consent. He walked around the shorter man to face his back. Reaching around to John's front, his fingers placed the tape measure at the widest part of his waist and slid around to the back again. It was pulled to the correct measurement and there was a moment of silence. Then the tape measure was dropped from John's waist and Sherlock strode back to the door of the bedroom while clicking his tongue. He opened it and said from the doorway, "I am pleased that we started this now. Any fatter and you might have become a lost cause."

The door was closed again and John sunk to the floor in an overwhelming mixture of relief and disappointment.

* * *

John had fallen asleep that night still topless and on the floor. When he woke up he had almost forgotten the whole occurrence. That is until he looked at himself in the mirror and sighed as it all came flooding back. He all of a sudden looked so much larger than he did yesterday. Can you gain weight in less than 12 hours?

_Don't be stupid, John, you're a doctor. You know you can't._

How was he going to face breakfast with Sherlock? He quickly dressed in a pair of jeans and the largest jumper he owned which still seemed to fit more snugly than he remembered. Taking a deep breath, he exited his bedroom and went to the kitchen.

Sherlock was sitting in his armchair with his arms resting around his violin. He appeared to be thinking and John had no desire to disturb him. He placed two pieces of bread in the toaster, turned the kettle on, and then waited as the two components of his breakfast heated.

"I'm surprised you are eating breakfast, John. Already given up on our plan?" called the snide voice from the living room.

"I can't not eat, Sherlock," he replied.

"You could if you were dedicated to the task."

John didn't want to give him the satisfaction of a response.

After a minute or so more of waiting his toast popped and the kettle started whistling. He poured himself a cup of tea and spread some butter on his toast before settling at the dining table. Ordinarily John would make room for himself by cautiously moving Sherlock's experiments out of the way but he did not care this morning. He haphazardly shoved everything to one side causing glass flasks and petri dishes to clink loudly against the microscope. The sound obviously caught Sherlock's attention because he was suddenly in the kitchen complaining about how people ought to be more careful. His eyes suddenly locked on John's breakfast.

"Interesting choice," he sneered.

"I have to eat something, Sherlock," said John tiredly.

"Did you put sugar in your tea?"

"Surely you could have worked that out yourself and no, I didn't. I never put sugar in my tea."

"I am merely asking because why not throw a few more calories in to your buttery breakfast?" said Sherlock in a harsh, mocking tone.

The alliteration temporarily distracted John and he did not respond for a moment. Apparently the moment was a moment too long as when he refocused, Sherlock was already walking out of the kitchen muttering something about how no one has any control over their appetites except for him.

John took a sip of his tea and looked down at the toast that had become soggy with melted butter. Any chance of feeling hungry had evaporated as soon as Sherlock had entered the kitchen. Sighing, he reluctantly dropped the toast into the bin and went to retrieve his laptop from the living room. John indirectly glanced at Sherlock and was sure that he had seen the ghost of a smirk hovering on his face.

* * *

**Author's note: Regarding the 'why?' of this fic, I don't really know for sure. I think it's because I like the occasional manipulative!Sherlock and I thought sooner or later he had to target John's weight?**

**I already have plans for my next fic which will be fluff/romance to the max so I think I was angsty the day this story was conceived. **


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